Preparation of [meso-tetraphenylchlorophinato]nickel(II) by stepwise deformylation of [meso-tetraphenyl-2,3-diformyl-secochlorinato]nickel(II): conformational consequences of breaking the structural integrity of nickel porphyrins

The stepwise, Wilkinson’s catalyst-induced decarbonylation of [meso-tetraphenyl-2,3-diformylsecochlorinato]Ni(II) (4) to produce the monoformylated pigment [meso-tetraphenyl-2-formylsecochlorinato] (5) and [meso-tetraphenylchlorophinato]Ni(II) (6) is described. Thus, we have shown how to degrade one pyrrolic unit of the starting material, [meso-tetraphenylporphyrinato]Ni(II) (2) in three steps to an aldimine linkage. The conformational changes of the porphyrinic macrocycle during the course of this degradation, as determined by comparison of the X-ray crystal structures of the compounds, are discussed. A comparative study delineates the UV–Vis spectroscopical consequences. In addition, the chemical reactivity of [meso-tetraphenylchlorophinato]Ni(II) (6) suggests the existence of an azepine-derived pyrrole-modified porphyrins (11, 12).